She should just be unfailingly chipper, start calling him "old man" all the time, and framing everything around his insecurities.
"How they danglin' Old Man?"
"Let the women speak, Gramps."
"This country's too big for those tiny hands, Old Man."
"Step aside and go yell at a cloud."
"Shouldn't you be lying about your golf scores somewhere?"
That's always his plan of attack, so you KNOW it works on him. Mockery and dismissal will have him weeping with frustrated confusion. We've already seen the best he's got is "No, YOU are."
The closest even TRUMP, piece-of-shit-manbaby-extraordinaire, has gotten to this to my knowledge is when he referred to Megyn Kelly's vagina as her "whatever". So no I don't agree this is "where we have been for a decade".
That would mean speaking a language he understands. Being civil and taking the high road allows him to bulldoze right in. Visibly dismissing him as any kind of serious contender removes his fangs.